POS1172 RISK OF VENOUS THROMBOEMBOLISM AFTER GOUT FLARES
Authors: E. Cipolletta, G. Nakafero, M. Mamas, A. Avery, L. Tata, A. Abhishek
Journal: Annals of the Rheumatic Diseases (2022)

Background Several population-based cohort studies have reported an increased risk of venous thromboembolism (VTE) in gout patients. However, none of these studies has investigated the temporal relationship between gout flares and VTE. Objectives To explore whether gout flares increase the risk of VTE in the short-term using the self-controlled case series (SCCS) method. Methods We identified participants with incident gout from the Clinical Practice Research Datalink (CPRD). Participants having less than one year of registration in CPRD and patients with a history of VTE or anticoagulant prescription more than one year before the first gout consultation were excluded. Participants with at least one gout flare and a diagnosis of VTE were selected. VTEs and gout flares were ascertained using primary care data, hospitalisation and mortality records, using previously validated algorithms (positive predictive value of 94% for VTE [1] and 68-95% for gout flares [2,3]). SCCS method involves fitting a Poisson model conditioned on the number of VTEs, and it calculates the adjusted incidence risk ratio (aIRR) and its 95% confidence interval (95%CI) for each stratum of the “at-risk” period as compared with the “baseline” period (Figure 1). The analysis was adjusted for age and calendar season. Figure 1. Schematic description of the observation period (“at-risk” and baseline periods). The “at-risk” period (in red) was defined as the period following the exposure (the gout flare), and it was subdivided as follows: days 0-30, 31-60 and 61-120 after each gout flare. The baseline period (in green) consisted of a pre-exposure and a post-exposure period of 365 days each. The length of each period varied according to the occurrence of the next flare and its timing. Panel A and panel B provide a schematic representation of patients with a single observation period and with multiple “non-overlapping” observation periods, respectively. In such cases, the length of the “at risk” period was 120 days, while the length of the pre-exposure and post-exposure period was 365 days each. Results Among the 104,962 patients with an incident diagnosis of gout in CPRD between 1997 and 2020, we identified 2,678 VTE (4.0 events/1,000 person-years). There were 53 VTE (13.3 events/month) during the “at-risk” period and 143 (6.0 events/month) during the “baseline” period (crude incidence rate ratio, 1.75; 95%CI: 1.27-2.42). The rates were highest in the first month after gout flares and then fell progressively (Table 1). Sensitivity analyses were consistent with the main analysis (Table 1). Table 1. Gout flare Number of events per month aIRR (95%CI ) p trend Main analysis 0-30 days 17.0 2.11 (1.27-3.50) 0.01 31-60 days 14.0 1.86 (1.07-3.24) 61-90 days 11.0 1.50 (0.95-2.37) Baseline period 6.0 Reference Sensitivity analysis (excluding participants with risk factors for VTE) [4] 0-30 days 14.0 3.13 (1.77-5.53) 0.01 31-60 days 7.0 1.66 (0.76-3.61) 61-90 days 8.0 1.75 (0.94-3.37) Baseline period 3.4 Reference Conclusion A transitory increase in the risk of VTE was observed after gout flares. References [1]Huerta C, et al. Risk factors and short-term mortality of venous thromboembolism diagnosed in the primary care setting in the United Kingdom. Arch Intern Med. 2007;167:935-43. [2]Zheng C, et al. Using natural language processing and machine learning to identify gout flares from electronic clinical notes. Arthritis Care Res (Hoboken). 2014;66:1740-8. [3]MacFarlane LA, Liu et al. Validation of claims-based algorithms for gout flares. Pharmacoepidemiol Drug Saf. 2016;25:820-6. [4]Konstantinides SV, et al. 2019 ESC Guidelines for the diagnosis and management of acute pulmonary embolism developed in collaboration with the European Respiratory Society (ERS). Eur Heart J. 2020;41:543-603. Disclosure of Interests None declared